This invention relates generally to apparatuses and methods for controllably and accurately conveying particulate materials. More specifically the invention concerns reliably conveying particulate materials from a particulate source container, such as a toner hopper, to subsequent unit operation process equipment. As an illustrative example, receiving receptacles on a fill line conveyor belt can receive particulates such as toner from a supply hopper by transport through a particulate conveyor article of the present invention and thereafter to a receiving manifold and subsequently to the toner receptacles. Other receivers can include a particulate mixer or formulating device, or a melt mixer or extruder device. The invention can be accomplished by fluidizing particulate materials and thereafter directing the resulting fluidized particulates to a fluidizing conveyor or conduit. The inner walls of the fluidizing conveyor article are highly porous, that is micro-porous, and permit a continuous stream of compressed gas to permeate the inner wall and into the interior cavity of the conduit to provide enhanced flow properties to the particulate materials.
A variety of particulate materials can be readily transported with the particulate conveyor apparatus of the present invention, for example, polymer particles and aggregates thereof such as lattices, toner particles, fine particle surface additives, such as hydrophilic or hydrophobic metal oxide particles, non magnetic particles, magnetic particles, fine powdered materials, such as food stuffs and pharmaceuticals, and mixtures thereof.
In embodiments the conveyor apparatus of the present invention can include: an optional fluidizing module for fluidizing otherwise non-fluid particulates received from a particle feed source; a fluidizing conduit article with gas permeable walls for fluidizing and controllably transporting the particulates from the source area or fluidizing area to an ultimate receiver vessel or subsequent unit operation; an optional receiver module for receiving the particulates from the fluidizing conduit article and to permit appropriate depressurization of the fluidized particulate stream; and optionally a low surface tension liner material in at least some portions of the fluidizing conduit which assists in the transport of particulates from the source to the receiver, for example, at connection points between the source or fluidizing module and the conduit, or between the conduit the receiver module. The low-friction low-surface tension or "non-stick" liner material further ensures continuous and non-blocking flow of particulate materials into, through, and out of the conduit article enabling smooth delivery of material and trouble free operation of the conveyor apparatus. The fluidizing conduit article or conveyor article of the present invention in conjunction with the particulate conveyor apparatus can provide exceptionally reliable particulate transport where, for example, clogging or particle flow inhibition of throughput rates are very low or eliminated; and high fill rates, high fill densities, and clean operation are consistently obtained. The article and apparatus provide for smooth, continuous flow, and high throughput of particulate materials.
The apparatus and method of the present invention solves important particulate transport problems and provides various advantages including: greatly reduced time required to transport particulate materials to receiving vessels in a continuous manner; and reduced downtime for blockage or leakage problems associated with continuous particle transport operations.
The apparatus and method of the present invention also prevents or greatly reduces wear of the conduit when abrasive particulates, such as magnetic particles and related abrasive particulates, are continuously conveyed and at high throughput velocities.
Problems associated with, for example, controlling the handling and filling of toner containers are largely attributable to the properties of the toner. Toner is the image-forming material in a developer which when deposited by the field of an electrostatic charge becomes the visible record. There are two main types of developing systems known as one-component and two-component systems. In one-component developing systems, the developer material is toner comprised of particles of magnetic material, usually iron, embedded in a black plastic resin. The iron enables the toner to be magnetically charged. In two-component systems, the developer material is comprised of toner of polymer or resin particles and a colorant, and a carrier of roughly spherical particles or beads usually made of steel. An electrostatic charge between the toner and the carrier bead causes the toner to cling to the carrier in the development process. Control of the flow of these small, abrasive and easily charged particles is very difficult. The one-component and two-component systems utilize toner that can be difficult to flow controllably. This is particularly true of the toner used in two component systems. The toner tends to cake and bridge within the hopper. This limits the flow of toner through the small tubes used for addition of the toner through the opening of the toner container. Also, this tendency to cake and bridge may cause air gaps to form in the container resulting in incorrect or partial filling of the container.
Attempts to improve the flow of toner and related particulate materials have also included the use of an external vibrating device to loosen the toner within the hopper and in conventional conduit conveyors. These vibrators are energy intensive, costly and not entirely effective and consistent. Other difficulties are also apparent in quickly starting and stopping the flow of toner from a hopper when filling a container with toner in a high speed production filling operation. A non-invasive electromagnetic toner valve in conjunction with an internal screw auger drive transport system has been developed and is described in the U.S. Pat. Nos. 5,685,348 and 5,839,485, the disclosures of which are incorporated herein by reference in their entirety.